Visitors to Sully Island saw at first hand the force of the incoming tide this weekend as part of a multiagency exercise. Three highly trained RNLI lifeguards, and two training mannequins were placed on the causeway just as the tide was starting to cover the rocks. Within a short period of time the mannequins were washed away, and the three lifeguards swept away into the strong currents. Both of Penarth's lifeboats, crewed by volunteers, were on standby to rescue the volunteers and recover the mannequins. In addition one lifeguard was winched by Coastguard Rescue Helicopter 187, and returned to the beach at Sully. This joint exercise also involved the coastguard rescue officers from Penarth and Barry, coastguard officers from Milford Haven, the national coast watch group from Nell's Point NCI and the South Wales Police drone unit.

Arranged chiefly as a combined exercise, visitors to the beach could be left in no doubt how quickly the tide comes in to cover the causeway - and the speed the 'casualties' were carried off by the tide.

Jason Dunlop, lifeboat operations manager for Penarth Station, said:'today's exercise demonstrated great partnership working, and showed how forceful the incoming tide is on the causeway. We used highly trained RNLI lifeguards as casualties, who were well equipped and well trained. People finding themselves trapped on the island should never attempt to make their way back across the causeway.'

Key facts about the RNLI

The Royal National Lifeboat Institution is the charity that saves lives at sea. Our volunteers provide a 24-hour search and rescue service in the United Kingdom and Ireland from 238 lifeboat stations, including four along the River Thames and inland lifeboat stations at Loch Ness, Lough Derg, Enniskillen and Lough Ree. Additionally the RNLI has more than 1,000 lifeguards on over 240 beaches around the UK and operates a specialist flood rescue team, which can respond anywhere across the UK and Ireland when inland flooding puts lives at risk.

The RNLI relies on public donations and legacies to maintain its rescue service. As a charity it is separate from, but works alongside, government-controlled and funded coastguard services. Since the RNLI was founded in 1824 our lifeboat crews and lifeguards have saved at least 140,000 lives. Volunteers make up 95% of the charity, including 4,600 volunteer lifeboat crew members and 3,000 volunteer shore crew. Additionally, tens of thousands of other dedicated volunteers raise funds and awareness, give safety advice, and help in our museums, shops and offices.